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Postgresql JDBC connection error on Android

I am unable to connect a PostgreSQL db on Android. Using JDBC is for development purpose only and will change to proper web service.
I have implemented the PostgreSQL driver in build.gradle as "implementation 'org.postgresql:postgresql:42.2.18.jre7"
My PostgreSQL database server is listening to port: 5433
My computer IP in my network is 192.168.1.103
And the user name and password is set correct
The connection:
Connection con = null;
try
{
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
/* Register jdbc driver class. */
Class.forName("org.postgresql.Driver");
/* Create connection url. */
String postgresConnUrl = "jdbc:postgresql://192.168.1.103:5433/lmsdb";
Properties props = new Properties();
props.setProperty("user","postgres");
props.setProperty("password","xxxxxxx");
props.setProperty("ssl","false");
/* Get the Connection object. */
con = DriverManager.getConnection(postgresConnUrl, props);
}catch(Exception ex)
{
ex.printStackTrace();
}finally
{
return con ;
}
When I change the IP in "postgresConnUrl" to 127.0.0.1 which is set in pg_hba, I get the error
org.postgresql.util.PSQLException: Connection refused. Check that the
hostname and port are correct and that the postmaster is accepting
TCP/IP connections
And when I use my computer's IP address as shown in the connection code above, the connection con = DriverManager.getConnection(postgresConnUrl, props); is returning null. The log shows no exception or errors, but the con is null and I am unable to trace the problem. Any directions to the problem would be helpful.

DriverManager.getConnection(...) cannot return null. Unless there is a severe bug in the implementation, it always returns a non-null connection or throws a SQLException (or RuntimeException or Error as thrown by drivers).
The PostgreSQL driver is likely causing an Error to be thrown (e.g. a NoClassDefFoundError, because the PostgreSQL JDBC driver uses Java features or classes not present on Android). This is hidden by the fact that your finally block will unconditionally return con, and you only catch and log instances of Exception, but not Error. See also Adding return in finally hides the exception
Remove your catch and finally block and let any exception or other Throwable bubble up to the caller, instead of replacing an explicit exception or error with a hidden error (returning null), alternatively have the catch block wrap the exception in a custom exception and throw that custom exception.
I recommend you don't use JDBC on Android. Most recent JDBC drivers are using Java features or classes not present on Android, which can cause all kinds of issues. You mention you're doing this for development purposes, but I would suggest that creating or mocking your REST API and using that from the start will save you a lot of headaches and unnecessary development work.

I tried using older version of JDBC and I was able to connect. The newer version of JDBC does not seem to be compatible with Android and result in error as you posted. But, still I can see many people are using JDBC as it is easy although Rest API is better option but requires additional skills.

No suitable driver found for jdbc:sqlserver:

I know this has been asked a hundred times and I think I have read all the posts and tried every variation of the solutions. I'm using NetBeans and new to it. I'm sure I'm just missing some small step because it seems like its just not seeing the driver that I added to the library. This is the first time I have tried to connect to a database so please be gentle.
try
{
String host = "jdbc:sqlserver://Server:1433;Database";
String uName = "User";
String uPass = "Password";
Connection con = DriverManager.getConnection(host,uName,uPass);
System.out.println("Your are connected to SQLServer 2014");
}
catch (SQLException err)
{
System.out.println(err.getMessage());
}

You forgot to register the jdbc driver class.
Call
Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
before calling Connection con = DriverManager.getConnection(host,uName,uPass);.
It will resolve the issue.
UPDATE
In documentation for new jdbc drivers it is declared that this step is not necessary. But in practical work, I have found that this step is required even for new drivers, otherwise you will get "No suitable driver found" error. This error occurs sometimes, for example it does not occur when you are making and running a console jar-application, but occurs when you have created and deployed a web-application.
So, I advise to register the jdbc driver class before getting the database connection via DriverManager.getConnection() call.

Cant connect to mariadb from java - only with mysqldeveloper [duplicate]

I am trying to connect to a database in Mariadb through a simple java application but the connection is told to be unsuccessful and an Exception is thrown. I have done the similar connection using mysql and it was working correctly. The problem is maybe with the driver here.
try{
Class.forName("org.mariadb.jdbc.Driver");
Connection connection = DriverManager.getConnection(
"jdbc:mariadb://localhost:3306/project", "root", "");
Statement statement = connection.createStatement();
String uname="xyz",pass="abc";
statement.executeUpdate("insert into user values('"+uname+"','"+pass+"')");}//end of try block
I looked up the internet for the help and came by that driver class provided by the MariaDB Client Library for Java Applications is not com.mysql.jdbc.Driver but org.mariadb.jdbc.Driver! I changed it accordingly but it seems the problem is with the very first line inside the try block. The driver is not loading at all.
Also, I have added the mysql jar file to the libraries of my java application as in the screen-shot below. Please help me through this.

It appears that you are trying to use jdbc:mariadb://... to establish a connection to a MariaDB server instance using the MySQL JDBC Driver. That probably won't work because the MySQL JDBC Driver would use jdbc:mysql://..., regardless of whether it is connecting to a MySQL server or a MariaDB server. That is, the connection string must match the driver that is being used (rather than the database server being accessed).
The MySQL and MariaDB drivers are supposed to be somewhat interchangeable, but it only seems prudent to use the MariaDB connector when accessing a MariaDB server. For what it's worth, the combination of mariadb-java-client-1.1.7.jar
and
Connection con = DriverManager.getConnection(
"jdbc:mariadb://localhost/project",
"root",
"whatever");
worked for me. I downloaded the MariaDB Client Library for Java from here:
https://downloads.mariadb.org/client-java/1.1.7/
which I arrived at via
https://downloads.mariadb.org/
Additional notes:
There is no need for a Class.forName() statement in your Java code.
The default configuration for MariaDB under Mageia may include the skip-networking directive in /etc/my.cnf. You will need to remove (or comment out) that directive if you want to connect to the database via JDBC because JDBC connections always look like "network" connections to MySQL/MariaDB, even if they are connections from localhost. (You may need to tweak the bind-address value to something like 0.0.0.0 as well.)

An additional note:
Exploring the MariaDB JDBC driver, I found this inside the url parsing file:
Project: https://github.com/MariaDB/mariadb-connector-j.git
File: src/main/java/org/mariadb/jdbc/UrlParser.java
public static UrlParser parse(final String url, Properties prop) throws SQLException {
....
if (url.startsWith("jdbc:mysql:")) {
UrlParser urlParser = new UrlParser();
parseInternal(urlParser, url, prop);
return urlParser;
} else {
if (url.startsWith("jdbc:mariadb:")) {
UrlParser urlParser = new UrlParser();
parseInternal(urlParser, "jdbc:mysql:" + url.substring(13), prop);
return urlParser;
}
}
As you can see, the string "jdbc:mariadb:" is always replaced with "jdbc:mysql:" internally. So when it comes to the MariaDB driver, whether it is :mariadb: or :mysql: it always gets parsed as "jdbc:mysql:".
No difference.
if (url.startsWith("jdbc:mariadb:")) {
....
parseInternal(urlParser, "jdbc:mysql:" + url.substring(13), prop);
....

Connecting MATLAB and MySQL with the JDBC Driver

I bought the book Undocumented MATLAB by Yair Altmam; in chapter 2.2 of the book he discusses database connectivity and using the JDBC to connect to databases. I followed the steps and text of the book. I downloaded the mysql-connector-java-5.1.30-bin.jar(from http://dev.mysql.com/downloads/connector/j/) and typed up the following code as detailed in the book:
clear all
%%Initializing JDBC driver
try
import java.sql.DriverManager;
javaclasspath('mysql-connector-java-5.1.30-bin.jar')
driverClassName = 'com.mysql.jdbc.Driver';
try
%This works when the class/JAR is on the static Java classpath
%Note: driver automatically registers with DriverManager
java.lang.Class.forName(driverClassName);
catch
try
%Try loading from the dynamic Java path
classLoader = com.mathworks.jmi.ClassLoaderManager.getClassLoaderManager;
driverClass = classLoader.loadClass(driverClassName);
catch %#ok<*CTCH>
try
%One more attempt, using the system class-loader
classLoader = java.lang.ClassLoader.getSystemClassLoader;
%An alternative, using the MATLAB Main Thread's context
%classLoader =
%java.lang.Thread.currentThread.getContextClassLoader;
driverClass = classLoader.loadClass(driverClassName);
catch
%One final attempt-load directly, like this:
driverClass = eval(driverClassName); %#ok<*NASGU>
%Or like this (if the driver name is known in advance):
driverClass = com.mysql.jdbc.Driver;
end
end
%Now manually register the driver with the DriverManager
%Note: silently fails if driver is not in the static classpath
DriverManager.registerDriver(driverClass.newInstance);
end
%continue with database processing
catch
error(['JDBC driver ' driverClassName ' not found!']);
%do some failover activity
end
%% Connecting to a database
import java.sql.*;
connStr = 'jdbc:mysql://localhost:3306/test';
con = DriverManager.getConnection(connStr,'root','1234');
Every attempt to run the code I get the following error message:
??? Java exception occurred:
java.sql.SQLException: No suitable driver found for
jdbc:mysql://localhost:3306/test
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
Error in ==> undocumentedMATLAB at 45
con = DriverManager.getConnection(connStr,'root','1234');
Has anyone experienced this problem or have any suggestion that could help me resolve it.
Thanks in advance.

My first suspicion is your java class path. Instead of:
javaclasspath('mysql-connector-java-5.1.30-bin.jar')
Use
javaaddpath('C:\full\path\to\mysql-connector-java-5.1.30-bin.jar')
If that is not the problem, lets skip the DriverManager (doesn't really help much) and see if the code below works, (or where it fails).
d = com.mysql.jdbc.Driver;
urlValid = d.acceptsURL('jdbc:mysql://localhost:3306/test'); %Should return true
props = java.util.Properties;
props.put('user','root'); props.put('password','1234');
con = d.connect('jdbc:mysql://localhost:3306/test',props)
The DriverManager construct doesn't really help much. It seems to be designed to allow a developer to load up a bunch of drivers, and then connect to any supported database without knowing or caring what the DB implementation was (e.g. Mysql, Postgresql, Oracle etc.) I have never seen this as a useful feature. I think (hope?) that this is being used less in favor of a DataSource construct.
Regardless, if this is your first time connecting Mysql to Matlab, you probably are best just directing using the provided Driver class.

"Data source name not found and no default driver"

java to mysql connection code:
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
System.out.println("Driver loaded");
con = DriverManager.getConnection(url, "root", "sai");
stmt = con.createStatement();
System.out.println("Connection established");
after excution of above code
"Driver loaded" message printed on console but,
after that following exception is printed -
[Microsoft][ODBC Driver Manager]
Data source name not found and no default driver specified
i have already create DSN(MYSQL ODBC 3.51 Driver) for project
Please tell me solution of above problem.

"If somehow possible, don't use a JdbcOdbc driver, but a pure JDBC-Driver for your database!"
An example MySql pure JDBC-Driver would be the com.mysql.jdbc.Driver class found in the mysql-connector-java-5.x.x.jar file available for download from MySQL.
A good explanation of the differences between JDBC and JDBC-ODBC are available on wikipedia

If somehow possible, don't use a JdbcOdbc driver, but a pure JDBC-Driver for your database!
For the question of how to register the driver, from the javadocs for java.sql, Interface Driver:
It is strongly recommended that each
Driver class should be small and
standalone so that the Driver class
can be loaded and queried without
bringing in vast quantities of
supporting code.
When a Driver class is loaded, it
should create an instance of itself
and register it with the
DriverManager. This means that a user
can load and register a driver by
calling
Class.forName("foo.bah.Driver")
A separate call to 'newInstance' or registerDriver' is Cargo-Cult-programming.

It's a while since I've done this, but you could try to explicitly register your driver with the DriverManager class. This means that you're not depending upon something unseen implicitly happening in the background.
DriverManager.registerDriver((Driver)
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver").newInstance());
con = DriverManager.getConnection(url, "root", "sai");
This will ensure that the "sun.jdbc.odbc.JdbcOdbcDriver" class is loaded and connected to the DriverManager.